The present disclosure relates to imaging devices, image processing methods, image processing programs, and semiconductor integrated circuits having image processing functions. More particularly, the present disclosure relates to image data size changing devices, electronic still cameras, image data size changing programs, semiconductor integrated circuits, etc., suited to reduction, enlargement, and distortion correction of an original image obtained from a single-sensor color imaging element.
There are known digital cameras which employ an imaging element, such as a CCD, a MOS sensor, etc., to capture an image of a subject through a shooting lens, and perform a predetermined image process with respect to image data output from the imaging element. A typical digital camera converts an image signal obtained from the imaging element into 10-, 12-, or 14-bit digital data, performs various image processes with respect to the digital data, compresses the resultant image data using a compression technique, such as JPEG encoding, etc., and records the compressed data to a recording medium. The recorded image has been subjected to various image processes, and therefore, if the user performs an additional image process with respect to a reproduced image, the image quality may be degraded.
A technique of outputting digital data obtained by converting an analog signal of each pixel output from the imaging element, without performing image processing with respect to the digital data inside the camera (such data is referred to as “RAW data”) is becoming popular as a function of single-lens reflex digital cameras. The RAW data is handled as follows. In the camera, the RAW data is recorded and maintained unprocessed. An external apparatus, such as a personal computer, etc., is used to reproduce (develop) an image from the RAW data. This enables the user to obtain a high-quality print of the image or to perform more sophisticated image editing which meets the user's requirements.
Imaging devices, such as those described above, include a color separation filter on an imaging element so as to capture a color image. For example, a color separation filter known as a Bayer filter includes primary color filters (i.e., red (R), green (G), and blue (B) color filters) arranged in a square grid, corresponding to pixels of the imaging element. Specifically, in the Bayer array, filters of the same color component are placed at every other pixel position along both the horizontal and vertical directions of the pixel array. Image data obtained through the color separation filter needs to be handled in a manner which maintains the Bayer pattern. If the Bayer pattern is disturbed, the color of a subject cannot be reproduced from the image data.
RAW-format data has a larger file size than that of JPEG-format data, etc., and therefore, it takes a longer time to reproduce RAW-format data. RAW data, which is original image data with a large size which has information about one color for each pixel, is reproduced by performing a synchronization process of obtaining information about R, G, or B for each pixel while performing gamma correction or achieving white balance, to obtain a final reproduced image. When the user wants to confirm the reproducibility of details of a subject, it is necessary to handle such a large-size image. On the other hand, for example, when the user wants to confirm only the reproducibility of colors (tone or feeling) or the result of changing of the level of brightness or gamma correction using, for example, the liquid crystal monitor of a digital camera, it is not necessary to use such a large image, and a small image is sufficient to confirm these things.
At present, the number of pixels in the imaging element is increasing and the high-speed read technique is advancing. Under these circumstances, when an image is captured in a record mode called small RAW in which the image is smaller than its original image or when a moving image having a standardized size, such as HD movie, is captured, a RAW image is reduced before a reproduction process or a recording process is performed, whereby a redundant process can be removed which would otherwise be performed in a subsequent process. Therefore, the processing time can be significantly reduced, and an approach to reduce the power consumption of the system can be taken.
As described above, a RAW image may be reduced so that the result of processing of RAW data is quickly displayed, the size of a preview image file is minimized, RAW-format data is recorded in the small RAW mode, a moving image having a standardized size is recorded, etc.
Conventionally, when RGB RAW data of an original image is resized, the RGB RAW data is separated into independent R, G, and B color data or pixel binning is performed by combining pixels of the same color, to perform decimation in the first process (see Japanese Patent Publication Nos. 2003-346143, 2001-245141, and 2002-84547). Alternatively, a full-size image is processed into YCrCb data, which is then put into a low-pass filter (LPF), and the resultant reduced-size data is recorded as a small RAW file (see Japanese Patent Publication No. 2007-158509).